solve aylei#8

Author: aylei

src/lib.rs

@@ -5,3 +5,5 @@ mod n0004_median_of_two_sorted_arrays;
 mod n0005_longest_palindromic_substring;
 mod n0006_zigzag_conversion;
 mod n0007_reverse_integer;
+mod n0008_string_to_integer_atoi;
+mod n0009_palindrome_number;

src/n0008_string_to_integer_atoi.rs

@@ -0,0 +1,117 @@
+/**
+ * [8] String to Integer (atoi)
+ *
+ * Implement <code><span>atoi</span></code> which converts a string to an integer.
+ * 
+ * The function first discards as many whitespace characters as necessary until the first non-whitespace character is found. Then, starting from this character, takes an optional initial plus or minus sign followed by as many numerical digits as possible, and interprets them as a numerical value.
+ * 
+ * The string can contain additional characters after those that form the integral number, which are ignored and have no effect on the behavior of this function.
+ * 
+ * If the first sequence of non-whitespace characters in str is not a valid integral number, or if no such sequence exists because either str is empty or it contains only whitespace characters, no conversion is performed.
+ * 
+ * If no valid conversion could be performed, a zero value is returned.
+ * 
+ * Note:
+ * 
+ * <ul>
+ * 	<li>Only the space character <code>&#39; &#39;</code> is considered as whitespace character.</li>
+ * 	<li>Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [-2^31,  2^31 - 1]. If the numerical value is out of the range of representable values, INT_MAX (2^31 - 1) or INT_MIN (-2^31) is returned.</li>
+ * </ul>
+ * 
+ * Example 1:
+ * 
+ * 
+ * Input: "42"
+ * Output: 42
+ * 
+ * 
+ * Example 2:
+ * 
+ * 
+ * Input: "   -42"
+ * Output: -42
+ * Explanation: The first non-whitespace character is &#39;-&#39;, which is the minus sign.
+ *              Then take as many numerical digits as possible, which gets 42.
+ * 
+ * 
+ * Example 3:
+ * 
+ * 
+ * Input: "4193 with words"
+ * Output: 4193
+ * Explanation: Conversion stops at digit &#39;3&#39; as the next character is not a numerical digit.
+ * 
+ * 
+ * Example 4:
+ * 
+ * 
+ * Input: "words and 987"
+ * Output: 0
+ * Explanation: The first non-whitespace character is &#39;w&#39;, which is not a numerical 
+ *              digit or a +/- sign. Therefore no valid conversion could be performed.
+ * 
+ * Example 5:
+ * 
+ * 
+ * Input: "-91283472332"
+ * Output: -2147483648
+ * Explanation: The number "-91283472332" is out of the range of a 32-bit signed integer.
+ *              Thefore INT_MIN (-2^31) is returned.
+ * 
+ */
+pub struct Solution {}
+
+// submission codes start here
+
+impl Solution {
+    pub fn my_atoi(input: String) -> i32 {
+        let (i32_min, i32_max) = (-2_i64.pow(31), 2_i64.pow(31) - 1);
+        let mut result: i64 = 0;
+        let mut minus = false;
+        // simple state machine
+        let mut num_matched = false;
+        for ch in input.chars().into_iter() {
+            if !num_matched {
+                match ch {
+                    ' ' => {},
+                    '0'...'9' => {
+                        num_matched = true;
+                        result = result * 10 + ch.to_digit(10).unwrap() as i64;
+                    },
+                    '-' => { num_matched = true; minus = true; }
+                    '+' => { num_matched = true; }
+                    _ => return 0
+                }
+            } else {
+                match ch {
+                    '0'...'9' => {
+                        result = result * 10 + ch.to_digit(10).unwrap() as i64;
+                        if result > i32_max { break }
+                    },
+                    _ => break
+                }
+            }
+        }
+        result = if minus { -result } else { result };
+        if result > i32_max { return i32_max as i32; }
+        if result < i32_min { return i32_min as i32; }
+        return result as i32;
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_8() {
+        assert_eq!(Solution::my_atoi("aa".to_string()), 0);
+        assert_eq!(Solution::my_atoi("-91283472332".to_string()), -2147483648);
+        assert_eq!(Solution::my_atoi("words and 987".to_string()), 0);
+        assert_eq!(Solution::my_atoi("4193 with words".to_string()), 4193);
+        assert_eq!(Solution::my_atoi("42".to_string()), 42);
+        assert_eq!(Solution::my_atoi("004193333".to_string()), 4193333);
+    }
+}

src/n0009_palindrome_number.rs

@@ -0,0 +1,53 @@
+/**
+ * [9] Palindrome Number
+ *
+ * Determine whether an integer is a palindrome. An integer is a palindrome when it reads the same backward as forward.
+ * 
+ * Example 1:
+ * 
+ * 
+ * Input: 121
+ * Output: true
+ * 
+ * 
+ * Example 2:
+ * 
+ * 
+ * Input: -121
+ * Output: false
+ * Explanation: From left to right, it reads -121. From right to left, it becomes 121-. Therefore it is not a palindrome.
+ * 
+ * 
+ * Example 3:
+ * 
+ * 
+ * Input: 10
+ * Output: false
+ * Explanation: Reads 01 from right to left. Therefore it is not a palindrome.
+ * 
+ * 
+ * Follow up:
+ * 
+ * Coud you solve it without converting the integer to a string?
+ * 
+ */
+pub struct Solution {}
+
+// submission codes start here
+
+impl Solution {
+    pub fn is_palindrome(x: i32) -> bool {
+        
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_9() {
+    }
+}